Coffee and reduction in death

Coffee is good. Coffee is bad. The studies bounce back and forth, but it is an important issue because 2.25 billion cups are drunk worldwide per day. So, benefit or harm has a huge impact on society. Some studies have shown a link between coffee consumption and lower levels of inflammation, insulin resistance, and risk for diabetes.

In this study, the researchers looked at coffee consumption and mortality—the ultimate endpoint.¹ First of all, the study was not funded by the coffee manufacturers. The data came from the EPIC (European Prospective Investigation into Cancer and Nutrition) study, which was tracking 521,330 people from 10 different European countries. The researchers compared mortality risk between non-coffee drinkers and coffee drinkers who consumed the highest amounts among the 41,693 people in the study who died over the course of 16.4 years.

All-cause mortality was reduced by 12% in men (HR, 0.88 [95% CI, 0.82–0.95]) and 7% in women (HR, 0.93 [CI, 0.87–0.98]). Mortality rates associated with digestive disease and cardiovascular disease represented the largest reductions. There was one bad signal for women, which was an increase in ovarian cancer–related death (HR, 1.31 [CI, 1.07-1.61]), but there was no obvious mechanism to explain this finding. For that matter, there are no definitive mechanisms to explain any of the death benefits. A subgroup of patients did have biomarker tests that evaluated liver enzymes, inflammatory markers, and A1c. All of them were reduced in the coffee vs non-coffee drinkers.

In the United States, using the data from the MEC Study (Multiethnic Cohort Study of Diet and Cancer), which was funded by the National Cancer Institute, the researchers found the same death reduction with coffee consumption.² Their database was over 185,000 people from different ethnic backgrounds who were followed for over 16 years. They found that one cup of coffee per day reduced death by 12% (HR, 0.88 [95% CI, 0.85–0.91]) and two to three cups per day reduced death by 18% (HR, 0.82 [CI, 0.79–0.86]). No benefit was gained with more than four cups per day versus two to three cups (HR, 0.82 [CI, 0.78–0.87]).

Interestingly, the trends were similar between drinkers of caffeinated and decaffeinated coffee, which means caffeine may not be the beneficial ingredient. This makes sense because there have been reports that very high caffeine consumption in the form of energy drinks is associated with harm. One suggested mechanism for coffee’s benefits is the polyphenol content in coffee. Polyphenols are very powerful antioxidants and perhaps they reduce vascular and DNA damage, and thereby reduce death.

Now, these studies are always thought-provoking but are never definitive because there are variables that we cannot control. For example, was it a black coffee or a double-double? The calorie content would be significantly different. Was the coffee consumed with friends sitting leisurely at a café or was it a cup of coffee between your knees that you sucked up with a straw as you weaved through rush hour traffic? The point is that these studies do have some flaws because you can’t get all the information from self-administered questionnaires.

However, it would be impossible to do a proper randomized trial with 20,000 people who drink two cups of coffee per day and 20,000 people who don’t drink any, and then follow them for 5 years and see which group suffered more deaths. That study is not going to happen. So, in the vacuum of no data, these studies are useful in giving us some direction.

For now, we can tell our patients that coffee consumption is not harmful (except for the small increase in ovarian cancer death). People need not feel guilty for having a coffee or two—they may live longer. But I would say limit the double-doubles and I would say sit back, relax, and enjoy the coffee. Maybe the important part in the “coffee break” is the “break” part. Enjoy your coffee.

References

1. Gunter MJ, Murphy N, Cross AJ, et al. Coffee drinking and mortality in 10 European countries: a multinational cohort study [published online July 11, 2017]. Ann Intern Med. doi:10.7326/M16-2945. http://annals.org/aim/article/2643435/coffee-drinking-mortality-10-european-countries-multinational-cohort-study
2. Park SY, Freedman ND, Haiman CA, et al. Association of coffee consumption with total and cause-specific mortality among nonwhite populations [published online July 11, 2017]. Ann Intern Med. doi:10.7326/M16-2472. http://annals.org/aim/article/2643433/association-coffee-consumption-total-cause-specific-mortality-among-nonwhite-populations

Abstract

BACKGROUND

The relationship between coffee consumption and mortality in diverse European populations with variable coffee preparation methods is unclear.

OBJECTIVE

To examine whether coffee consumption is associated with all-cause and cause-specific mortality.

DESIGN

Prospective cohort study.

SETTING

10 European countries.

PARTICIPANTS

521 330 persons enrolled in EPIC (European Prospective Investigation into Cancer and Nutrition).

MEASUREMENTS

Hazard ratios (HRs) and 95% CIs estimated using multivariable Cox proportional hazards models. The association of coffee consumption with serum biomarkers of liver function, inflammation, and metabolic health was evaluated in the EPIC Biomarkers subcohort (n = 14 800).

RESULTS

During a mean follow-up of 16.4 years, 41 693 deaths occurred. Compared with nonconsumers, participants in the highest quartile of coffee consumption had statistically significantly lower all-cause mortality (men: HR, 0.88 [95% CI, 0.82 to 0.95]; P for trend < 0.001; women: HR, 0.93 [CI, 0.87 to 0.98]; P for trend = 0.009). Inverse associations were also observed for digestive disease mortality for men (HR, 0.41 [CI, 0.32 to 0.54]; P for trend < 0.001) and women (HR, 0.60 [CI, 0.46 to 0.78]; P for trend < 0.001). Among women, there was a statistically significant inverse association of coffee drinking with circulatory disease mortality (HR, 0.78 [CI, 0.68 to 0.90]; P for trend < 0.001) and cerebrovascular disease mortality (HR, 0.70 [CI, 0.55 to 0.90]; P for trend = 0.002) and a positive association with ovarian cancer mortality (HR, 1.31 [CI, 1.07 to 1.61]; P for trend = 0.015). In the EPIC Biomarkers subcohort, higher coffee consumption was associated with lower serum alkaline phosphatase; alanine aminotransferase; aspartate aminotransferase; γ-glutamyltransferase; and, in women, C-reactive protein, lipoprotein(a), and glycated hemoglobin levels.

LIMITATIONS

Reverse causality may have biased the findings; however, results did not differ after exclusion of participants who died within 8 years of baseline. Coffee-drinking habits were assessed only once.

CONCLUSION

Coffee drinking was associated with reduced risk for death from various causes. This relationship did not vary by country.

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